(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization International Bureau (43) International Publication Date PCT (10) International Publication Number 27 March 2008 (27.03.2008) WO 2008/035153 A2 (51) International Patent Classiflcation: Not classified Pharmaceuticals Ltd., 476/14, Old Mahabalipuram Road, Sholinganallur, Chennai 600 119, Tamil Nadu (IN). (21) International Application Number: PCT/IB2007/002192 (74) Agents: GOPALAN,Deepak, Sriniwas et al.; K & S Part ners, 84-C, C-6 Lane, Off Central Avenue, Sainik Farms, (22) International Filing Date: 31 July 2007 (3 1.07.2007) New Delhi 110 062 (IN). (25) Filing Language: English (81) Designated States (unless otherwise indicated, for every kind of national protection available): AE, AG, AL, AM, AT,AU, AZ, BA, BB, BG, BH, BR, BW, BY,BZ, CA, CH, (26) Publication Language: English CN, CO, CR, CU, CZ, DE, DK, DM, DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, HN, HR, HU, ID, IL, (30) Priority Data: IN, IS, JP, KE, KG, KM, KN, KP, KR, KZ, LA, LC, LK, 1369/CHE/2006 2 August 2006 (02.08.2006) IN LR, LS, LT, LU, LY,MA, MD, ME, MG, MK, MN, MW, 1779/CHE/2006 MX, MY, MZ, NA, NG, NI, NO, NZ, OM, PG, PH, PL, 27 September 2006 (27.09.2006) IN PT, RO, RS, RU, SC, SD, SE, SG, SK, SL, SM, SV, SY, TJ, TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN, ZA, (71) Applicant (for all designated States except US): ORCHID ZM, ZW CHEMICALS & PHARMACEUTICALS LIMITED [IN/IN]; Orchid Towers, 313 Valluvar Kottam High Road, (84) Designated States (unless otherwise indicated, for every Nungambakkam, Chennai 600 034, Tamil Nadu (IN). kind of regional protection available): ARIPO (BW, GH, GM, KE, LS, MW, MZ, NA, SD, SL, SZ, TZ, UG, ZM, (72) Inventors; and ZW), Eurasian (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), (75) Inventors/Applicants (for US only): European (AT,BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, GNANAPRAKASAM, Andrew [IN/IN]; Orchid FR, GB, GR, HU, IE, IS, IT, LT,LU, LV,MC, MT, NL, PL, Chemicals & Pharmaceuticals Ltd., 476/14, Old PT, RO, SE, SI, SK, TR), OAPI (BF, BJ, CF, CG, CI, CM, Mahabalipuram Road, Sholinganallur, Chennai 600 119, GA, GN, GQ, GW, ML, MR, NE, SN, TD, TG). Tamil Nadu (IN). VENUGOPAL, Sivasankaran [IN/IN]; Orchid Chemicals & Pharmaceuticals Ltd., 476/14, Old Declaration under Rule 4.17: Mahabalipuram Road, Sholinganallur, Chennai 600 119, — as to the applicant's entitlement to claim the priority of the Tamil Nadu (IN). GANAPATHY, Veeramani [IN/IN]; earlier application (Rule 4.17(Ui)) Orchid Chemicals & Pharmaceuticals Ltd., 476/14, Old Mahabalipuram Road, Sholinganallur, Chennai Published: 600 119, Tamil Nadu (IN). UDAYAMPALAYAM, — without international search report and to be republished Palanisamy, Senthilkumar [IN/IN]; Orchid Chemicals & upon receipt of that report (54) Title: PROCESS FOR THE PREPARATION OF BETA-LACTAM ANTIBIOTIC (57) Abstract: Novel process for the preparation of the Faropenem of formula (I) where, R is hydrogen, alkali metal salts such as sodium or potassium, or prodrug residue. PROCESS FOR THE PREPARATIONOF β-LACTAM ANTIBIOTIC Field An improved process relating to the preparation of β-lactam antibiotic of formula (I) or its hydrate in a pure form is described. The compound of formula (I) is known as Faropenem, wherein, R is hydrogen, alkali metal salts such as sodium or potassium, or prodrug residue. Background Faropenem is an orally active β-lactam antibiotic belonging to the penem group. Faropenem is chemically known as 6-(l-hydroxyethyl)-7-oxo-3-(oxolan- 2-yl)-4-thia-l-azabicyclo[3.2.0]hept-2-ene-2-carboxylicacid. The known forms of Faropenem are Faropenem sodium and the prodrug form, Faropenem Medoxomil (also known as Faropenem Daloxate). In view of the importance of the compound of the formula (I), several synthetic procedures to prepare the compound have been reported. US 4,997,829 provides process for the preparation of faropenem according to the following scheme. The process is exemplified with the allyl protected carboxyl group. One of the process involves the reaction of A- acetoxyazetidinone with tetrahydrothiofuroic acid, condensation with allyl glyoxalate in refluxing benzene, chlorination with thionyl chloride, reaction of triphenylphosphine with lutidine in hot THF, cyclization in refluxing toluene, deprotection of silyl protecting group with tetrabutylammonium fluoride, treating with triphenylphosphine and, treating with sodium 2-ethylhexanoate and (PP ) Pd to result faropenem sodium. The process exemplified utilizes benzene as solvent, which is not environmentally acceptable. Tetrabutylammonium fluoride was used as desilylating agent that is expensive. Even though the description teaches that optically active compounds can be employed, the examples utilized the dl-compound of tetrahydrothiofuroic acid further requiring resolution. Methods are provided for the synthesis of series of penem compounds in J Antibiotics 1988, 41(11), 1685-1693. The provided methods utilize sulfonylazetidinone as the starting materials. As one of the procedures gives lesser yield, another procedure was adopted which uses silver salts. Japanese patent, JP2949363 describes a process for deallylation and salt formation with an alkali metal salt of carboxylic acid in the presence of a catalytic amount of palladium complex for the preparation of faropenem. EP410727 describes a process for removing allyl group from a penem compound using cyclic 1,3-diketone such as dimedone. The yield and quality of the final product is always less in the above prior art methods. With the continued research, the present inventors have undertaken extensive studies for developing a process for the preparation of compound of formula (I), which is commercially viable, involves simple techniques such as crystallizations, with improved yields and quality of the product, and with lesser reaction time. None of the prior art suggests or teaches the techniques provided herein. Objectives The main objective herein is to provide a simple and commercially viable process for the preparation of compound of the formula (I) in pure form. Another objective is to provide starting materials, intermediates and the final product in crystalline solids, which in turn provides improved purity and stability. Another objective herein is to provide a simple and commercially viable process for the preparation of compound of the formula (I), which avoids chromatographic purification techniques. Summary Process for the preparation of faropenem of formula (I), which comprises the steps of: (a) reacting 4-acetoxyazetidinone (II) (AOSA) with alkali metal salt of tetrahydrothiofuroic acid of compound formula (III) in a solvent in presence or absence of base to produce the compound of formula (IV), (b) condensing the compound of formula (TV) with oxalyl chloride of formula (V) wherein R' is p-nitrobenzyl (PNB), p-methoxybenzyl (PMB), p-nitrophenyl (PNP), p-methoxyphenyl (PMP), 3,4- dimethoxybenzyl, allyl, t-butyl, trityl, benzyl, benzhydryl (BH), or silyl and the like in presence or absence of base to produce compound of formula (VI). (c) cyclizing the compound of formula (VI) wherein R' is as defined above in presence or absence of solvent and in presence trialkyl-, triaryl-, or trialkylaryl-phosphite to compound of formula (VII), (d) deprotecting the compound of formula (VII), and (e) isolating faropenem or its salts of compound of formula (I). The process is shown in Scheme-I as given below: Brief description of the drawings Figure 1: PXRD pattern of sodium salt of R(+)-tetrahydrofuran-2-thiocarboxylic acid. Figure 2 : PXRD pattern of compound of formula (IV). Figure 3: PXRD pattern of compound of formula (VI). Figure 4 : PXRD pattern of diprotected faropenem of compound of formula (VII). Figure 5: PXRD pattern of compound of formula (VIII). Figure 6: PXRD pattern of Faropenem sodium of compound of formula (I). Figure 7: IR spectrum of sodium salt of R(+)-tetrahydrofuran-2-thiocarboxylic acid. Figure 8: IR spectrum of compound of formula (IV). Figure 9: IR spectrum of compound of formula (VI). Figure 10: IR spectrum of diprotected faropenem of compound of formula (VII). Figure 11: IR spectrum of compound of formula (VIII). Figure 12: IR spectrum of Faropenem sodium of compound of formula (I). Description In a first embodiment, alkali metal salt of R(+)-tetrahydrofuran-2- thiocarboxylic acid of formula (III) preferably as a sodium salt was reacted with acetylazetidinone of compound of formula (II) in step (a) to form a compound of formula (IV), which is isolated as a crystalline solid. The reaction was also performed without isolating compound of formula (IV) as described in the example of one-pot process. It was surprisingly found that the use of sodium salt of R(+)-tetrahydrofuran-2-thiocarboxylic acid than the in situ generated one has more advantages in terms of better yield and complete conversion to product to obtain compound of formula (IV). The handling of solid sodium salt of R(+)- tetrahydrofuran-2-thiocarboxylic acid is easier and industrially advantageous than the liquid R(+)-tetrahydrofuran-2-thiocarboxylic acid and moreover the high purity of sodium salt avoids the formation of undesired products. The malodorous nature of the R(+)-tetrahydrofuran-2-thiocarboxylic acid is avoided by using its sodium salt. The compound of formula thus obtained following step (a) is crystalline in nature as evidenced from Powder X-Ray Diffraction (PXRD) and is shown in Figure 2. The compound of formula (IV) is then converted to faropenem compound of formula (I) as given in scheme I, wherein the solvent used in step (a) is selected from acetone, dioxane, tetrahydrofuran (THF), water, diglyme, monoglyme, toluene and the like or the mixture thereof and the base used in step (a) is selected from inorganic base such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate and the like. The base used in step (b) is selected from triethylamine, diisopropylethylamine, diisopropylamine, diethylamine, tetramethylguanidine (TMG), l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), l,5~diazabicyclo[4.3.0]non~5-ene (DBN), ammonia and the like or mixture thereof.